Rabeprazole, 2-[[[4-(3-Methoxypropoxy)-3-methyl-2-pyridinyl]methyl]sulfinyl]-1H-benzimidazole has the following structural formula

Rabeprazole belongs to a class of antisecretory compounds (substituted benzimidazole proton-pump inhibitors) that do not exhibit anticholinergic or histamine H2-receptor antagonist properties, but suppress gastric acid secretion by inhibiting the gastric H+, K+ ATPase at the secretory surface of the gastric parietal cell. Because this enzyme is regarded as the acid (proton) pump within the parietal cell, rabeprazole has been characterized as a gastric proton-pump inhibitor. Rabeprazole blocks the final step of gastric acid secretion. So that it can effectively inhibit the secretion of an acid and is therefore effective in the therapy or prevention of human and animal peptic ulcer.
The U.S. Pat. No. 5,045,552 discloses the Rabeprazole and many other substituted benzimidazole-type compounds having anti-ulcer activity. This patent further discloses the process for preparation of Rabeprazole by oxidation of Rabeprazole sulfide using 85% m-chloroperbenzoic acid in a mixture of dichloromethane and diethyl ether followed by work up to get product as oil. The obtained oil is crystallized from a mixture of dichloromethane/ether. Optionally the oily crude is dissolved in aqueous solution of sodium hydroxide. The obtained solution is subjected to azeotropic distillation with ethanol to remove water and adding ether to get crystalline Rabeprazole base.

According to the prior art, Rabeprazole base is crystallized using dichloromethane/ether to obtain crystalline off white product. The HPLC purity is less than or equal to 99% and the isolation procedure involves azeotropic distillation of water, during which the product is exposed to high temperature and leads to certain impurities. Repeated crystallization is needed to remove impurities to get desired quality. Using large volumes of chlorinated solvents in the plant leads to environmental hazardous.
Japanese patent application JP2001039975 teaches that the product obtained by example 33 of U.S. Pat. No. 5,045,552 with a melting range of 140-141° C. corresponds to amorphous rabeprazole sodium
The U.S. Pat. No. 6,919,459 patent also discloses the process for the preparation of Rabeprazole by oxidation of Rabeprazole sulfide using m-Chloroperbenzoic acid (m-CPBA) in a suitable solvent. The reaction mass is subjected to repeated washings at different pH levels and isolate the product from aqueous layer.

Rabeprazole is not stable at acidic conditions and decomposes to form unknown impurities. To remove these impurities repeated crystallizations are required to get desire quality of the final product.
The WO2006/117802 PCT application discloses the process for the preparation of Rabeprazole sodium by oxidation of Rabeprazole sulfide with sodium hypo halite solution in water or a mixture of water and water miscible solvent medium using alkali metal hydroxide and catalyst. The reaction mass is saturated by inorganic saturating agents and the Rabeprazole sodium salt is extracted with water immiscible organic solvent. Organic solvent is distilled and the residue is dissolved in second organic solvent to get clear solution, which is precipitated by adding antisolvent.
The WO2006/120701 PCT application discloses process for manufacture of amorphous Rabeprazole sodium by the reaction of Rabeprazole base with aqueous sodium hydroxide. Ethanol is added to the obtained solution. Solvents are distilled from the solution to get thick mass. Organic solvent is added to the obtained residue to get clear solution, to which antisolvent is added to get amorphous Rabeprazole sodium.
The prior art methods cited above have many disadvantages, these methods involve more number of organic solvents and lack successive extractions and washings of the layers during work up procedure. It leads to many impurities that ultimately affect on purity and yield loss of final product.
The U.S. Pat. No. 6,180,652 and WO 2003101452 PCT application discloses the process for the preparation of amorphous rabeprazole sodium, which is obtained by lyophilization of an aqueous solution of rabeprazole sodium acetone complex and an aqueous NaOH solution of Rabeprazole respectively.

Lyophilization technique is not suitable for production at industrial scale and it needs more time cycle and involves the cost.
We observed that rabeprazole is rapidly degraded in chlorinated solvent like dichloromethane to form unknown impurities, due to impurities while distillation gummy material is formed. It leads to yellowish color in final product, finally it leads to yield loss in final product.
According to prior art methods,                (a) Dichloromethane/ether is used for final crystallization gives off white product with HPLC purity less than or equal to 99% and        (b) Rabeprazole sodium is isolated by using azeotropic distillation. It needs high temperature to remove water and the reaction mass is exposed to high temperature to form unknown impurities, to remove these impurities repeated crystallizations are required to get desire quality of the final product.        
To overcome all above problems there is a need to develop such a process which is plant friendly and gives extra pure and white colored Rabeprazole base and subsequent sodium salt